thermoregulation

High body temperature. If the body
is too hot, blood vessels dilate to let more blood reach the skin,
where the blood cools. This causes the skin to look flushed. Sweat
glands produce more sweat, which evaporates to cool the skin.

Low body temperature. If the body
is too cold, the blood vessels narrow. The arrector pili muscles contract,
lifting hairs and pulling on the skin to form goose pimples. The erect
hairs trap an insulating layer of air next to the skin.

Thermoregulation is the body's internal, automatic temperature regulating mechanism,
which is controlled by the hypothalamus in the brain.

The skin plays a significant
role in regulating body temperature.
In contrast with some animals, humans do not possess a thick fur coat to
provide warmth. Instead, we have a complex thermoregulation system that
includes features such as special blood vessels in the skin that are concerned
solely with conservation and loss of heat. A layer of fat under the skin
provides extra insulation.